Single 10 Shunt Fed Hartley Oscillator for 80 meter CW

  
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This Hartley oscillator was built on the remains of a single tube Hartley using a single 45. The original circuit I constructed was one that was published in a 1932 QST article by George Grammer. As it turned out, both of the 45s I had were weak, so the oscillator only would run when it was loaded very, very lightly. I did, however, have a good 10
Single 10 Shunt Fed Hartley Oscillator for 80 meter CW - schematic

triode, so I decided to change the value of the grid leak and the element voltages accordingly, and stick a 10 in the circuit. The 10 was a very popular tube in the late 20`s and early 30s for use in simple amateur radio transmitters. Sterlings "Radio Manual", second edition, 1929, has a section devoted to a shunt-fed hartley oscillator using a 10 triode. This same book, incidentally, has a section devoted to a simple three tube regenerative receiver, using tube base coils. You can build a complete 1929 station with the info in this book! Anyway, this tube oscillated easily and I was able to get 5 watts, output, when loaded, using 300 VDC on the plate. But, on key-up, the tube drew a slight amount of current, which turned out to be a parasitic oscillation. I was, however, quite happy with the output power and efficiency of the 10 in this circuit. My success with the shunt-fed design using 27s, shown elsewhere on this site, convinced me to re-build the Grammer Hartley using a 10 in the shunt-fed configuration. I wanted to change my original wire tank coil with more period-looking copper tubing anyway. So, here is the schematic of the single 10 Hartley oscillator: I built the circuit breadboard style on a piece of poplar. The front panel is a kind of acrylic product that I bought at the local electronics surplus store. It sort of looks like bakelite, which was the appearance I was after. The vintage National Dial I picked up...



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